1. Field of the Invention
The present invention relates to a process for the recovery of m-ethylphenol, and more particularly, relates to a process for the recovery of high-purity m-ethylphenol by contacting a mixture of ethylphenols containing m- and p-ethylphenols with a specific catalyst under heating, thereby selectively dealkylating p-ethylphenol to phenol and ethylene.
m-Ethylphenol is useful as an intermediate for the production of pharmaceuticals and agricultural chemicals. Since pharmaceuticals and agricultural chemicals are related directly or indirectly to human lives, the presence of impurities in the products is not permissible. Thus, raw materials and intermediates with a purity as high as possible are desired for the production of pharmaceuticals and agricultural chemicals, and therefore, high-purity m-ethylphenol is required when it is used as an intermediate for the production of pharmaceuticals and agricultural chemicals.
2. Description of the Prior Art
The conventional process for the preparation of m-ethylphenol comprises sulfonation of ethylbenzene, hydrolysis of the thus produced ethylbenzenesulfonic acid mixture excepting the m-isomer, and alkali fusion of the remaining m-ethylbenzenesulfonic acid. This process has long been practiced industrially.
It is also known that a mixture of ethylphenol isomers is obtained by alkylation of phenol with ethylene, ethanol, etc. (Japanese Patent Publication No. Sho 44(1969)-53; U.S. Pat. No. 4,532,368). However, among the ethylphenols, m-ethylphenol and p-ethylphenol have very close boiling points, and it is practically impossible to isolate m-ethylphenol from a mixture of ethylphenols by distillation. No industrial process has been known which allows purification of m-ethylphenol from ethylated products of phenol.
Development of a new process of preparation of m-ethylphenol has been desired because the conventional process of its preparation from ethylbenzene via ethylbenzenesulfonic acid has many problems such as tedious multi-step operation, inferior operational surroundings associated with handling of dangerous high-temperature sulfuric acid and sodium hydroxide, corrosion of equipment caused by the use of sulfuric acid, and disposal of waste water containing sulfuric acid and alkali.
On the other hand, the ethylation of phenol is advantageous for the preparation of an ethylphenol mixture because it requires fewer steps and simpler operation. This process, however, does not permit selective preparation of high-purity m-ethylphenol because it is difficult to separate m-ethylphenol and p-ethylphenol contained in the product mixture.